Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$175.89	11.700%	$196.4691	$196.47	$196.45	$196.50
Purchase #2	$237.27	5.525%	$250.3792	$250.38	$250.40	$250.40
Purchase #3	$116.66	8.423%	$126.4863	$126.49	$126.50	$126.50
Purchase #4	$15.88	3.160%	$16.3818	$16.38	$16.40	$16.40
Purchase #5	$202.83	8.213%	$219.4884	$219.49	$219.50	$219.50
Purchase #6	$225.89	10.722%	$250.1099	$250.11	$250.10	$250.10
Purchase #7	$106.66	9.297%	$116.5762	$116.58	$116.60	$116.60
7 purchase totals =	$1,081.08		$1,175.8909	$1,175.90	$1,175.95	$1,176.00